1. Field of the Invention
The present invention relates to a method for the renaturation of denatured proteins by treatment with a renaturant.
2. Description of the Related Art
A wide variety of types of proteins which occur in plant and animal organisms and have various types of effects on the structure, the function and the metabolism of the cells are prone to lose, under various influences, their natural three-dimensional folding pattern, which is called the secondary structure, and to become denatured. The denaturation includes breakdown of the intramolecular interaction, especially hydrogen bonds, and thus loss of the .alpha.-helix structure which virtually all native proteins have, at least in parts of the molecule, and which, as part of the secondary structure, is decisively responsible for the activity of the protein.
One of the influences leading to denaturation is heating to a temperature which may be up to 150.degree. C., depending on the protein. Other influences of this type are changes in the pH to below 3 or above 9, addition of denaturing reagents such as urea, guanidine or amide solutions, introduction into foaming solutions, spreading on surfaces, irradiation with UV or X-rays or use of wetting agents.
It is not uncommon in industry for proteins to be unintentionally but unavoidably denatured because their environment is, for other reasons, subjected to conditions under which denaturation takes place. One example thereof is steam sterilization of biomaterials, in which proteins immobilized thereon are denatured. Another example is UV irradiation of polymer surfaces with proteins adsorbed or immobilized thereon to prepare for grafting with monomers intended to modify the surface properties. Valuable proteins such as blood proteins may furthermore undergo unwanted denaturation, for example by the pH getting into the dangerous range on binding to and modification of surfaces.
It is known that trifluoroethanol preserves the secondary and tertiary structure of proteins (F. D. Sonnichsen et al., Biochemistry 1992, 31, 8790-8798; J. S. Albart et al., Biochemistry 1995, 34, 984-990; A. Cammers-Goodwin et al., J. Am. Chem. Soc. 1996, 118, 3082-2890) and, furthermore, induces non-specific helical foldings, so that the resulting proteins have different dominant folding patterns and are thereby denatured (A. J. Arunkumar et al., Biochimica et Biophysica Acta 1997, 1338, 69-79).